What is PGT-A?

PGT-A is a method for assessing the genetic material inside an embryo. This material is contained within structures known as Chromosomes. Humans have 22 pairs of chromosomes plus a pair of sex chromosomes (XX for females and XY for males). Embryos with the correct number of chromosomes (known as Euploid embryos) have a better chance of establishing a healthy pregnancy than those with an abnormal number.


The above is a diagram showing an extra copy (trisomy) of chromosome 16.


Could PGT-A be right for me?

Because older women are more likely to have eggs with the wrong number of chromosomes, PGT-A has  traditionally been offered to women over  the age of 37. Having eggs, and hence embryos, with the wrong number of chromosmes is thought to be one of the  main reasons why older women can find it difficult to conceive, are more likely to have a miscarriage and are more likely to have a baby affected by Down's Syndrome.

You  may also wish to consider PGT-A if you or your partner have a family history of chromosome problems (some translocations) or if you have had several unexplained miscarriages or failed IVF attempts

How is PGT-A done

PGT-A is an adjunct to standard IVF/ ICSI treatment. Embryos are cultured for 5 days and at that point are assessed for quality and whether they are suitable for biopsy. If the embryos are suitable a small number of cells are removed from the outer membrane of the embryos, known as the trophectoderm, (which later develops into the placenta). Those trophectoderm cells are then sent to a specialist genetics testing laboratory for analysis. Meanwhile the embryos are frozen to allow enough time for the analysis to be done. WFI will receive the results after a few weeks.

There are 4 outcomes to PGT-A testing of embryos. Embryos can be

  • Euploid - biospsied cells having the correct number of chromosomes - these can be transferred.
  • Aneuploid - biopsied cells having an incorrect number of chromosomes - these cannot be transferred.
  • Mosaic - biopsied cells having a mixture of euploid and aneuploid cells - these may be able to be transferred under limited circumstances.
  • No Result - biopsied cells not having any results after testing - these may be able to be transferred under limited circumstances.

Once the results are known and have been discussed with you and you have some suitable embryos we can then plan your embryo transfer at a convenient time    

Does PGT-A testing work?

The detection of aneuploidy in cells is quite complex and relies on several different factors. Embryos may not be suitable for biopsy; results from the testing procedure may not be conclusive. There is mixed scientific data about PGT-A. Large scale trials of IVF aneuploidy testing have yet to be done, though small scale trials have shown benefits in certain patients groups.  The HFEA has further information on aneuploidy testing here